The number of the mammiferous remains embedded in the Pampas is, as I have remarked, wonderful: it should be borne in mind that they have almost exclusively been found in the cliffs and steep banks of rivers, and that, until lately, they excited no attention amongst the inhabitants: I am firmly convinced that a deep trench could not be cut in any line across the Pampas, without intersecting the remains of some quadruped.It is difficult to form an opinion in what part of the Pampas they are most numerous; in a limited spot they could not well have been more numerous than they were at P.Alta; the number, however, lately found by Senor F.Muniz, near Luxan, in a central spot in the Pampas, is extraordinarily great: at the end of this chapter I will give a list of all the localities at which I have heard of remains having been discovered.Very frequently the remains consist of almost perfect skeletons; but there are, also, numerous single bones, as for instance at St.Fe.Their state of preservation varies much, even when embedded near each other: I saw none others so perfectly preserved as the heads of the Toxodon and Mylodon from the white soft earthy bed on the Sarandis in Banda Oriental.It is remarkable that in two limited sections Ifound no less than five teeth separately embedded, and I heard of teeth having been similarly found in other parts: may we suppose that the skeletons or heads were for a long time gently drifted by currents over the soft muddy bottom, and that the teeth occasionally, here and there, dropped out?
It may be naturally asked, where did these numerous animals live? From the remarkable discoveries of MM.Lund and Clausen, it appears that some of the species found in the Pampas inhabited the highlands of Brazil: the Mastodon Andium is embedded at great heights in the Cordillera from north of the equator to at least as far south as Tarija (Humboldt states that the Mastodon has been discovered in New Granada: it has been found in Quito.
When at Lima, I saw a tooth of a Mastodon in the possession of Don M.
Rivero, found at Playa Chica on the Maranon, near the Guallaga.Every one has heard of the numerous remains of Mastodon in Bolivia.); and as there is no higher land, there can be little doubt that this Mastodon must have lived on the plains and valleys of that great range.These countries, however, appear too far distant for the habitation of the individuals entombed in the Pampas: we must probably look to nearer points, for instance to the province of Corrientes, which, as already remarked, is said not to be covered by the Pampean formation, and may therefore, at the period of its deposition, have existed as dry land.I have already given my reasons for believing that the animals embedded at M.Hermoso and at P.
Alta in Bahia Blanca, lived on adjoining land, formed of parts of the already elevated Pampean deposit.With respect to the food of these many great extinct quadrupeds, I will not repeat the facts given in my "Journal"(second edition page 85), showing that there is no correlation between the luxuriance of the vegetation of a country and the size of its mammiferous inhabitants.I do not doubt that large animals could now exist, as far as the amount, not kind, of vegetation is concerned, on the sterile plains of Bahia Blanca and of the R.Negro, as well as on the equally, if not more sterile plains of Southern Africa.The climate, however, may perhaps have somewhat deteriorated since the mammifers embedded at Bahia Blanca lived there; for we must not infer, from the continued existence of the same shells on the present coasts, that there has been no change in climate; for several of these shells now range northward along the shores of Brazil, where the most luxuriant vegetation flourishes under a tropical temperature.With respect to the extinction, which at first fills the mind with astonishment, of the many great and small mammifers of this period, Imay also refer to the work above cited (second edition page 173), in which I have endeavoured to show, that however unable we may be to explain the precise cause, we ought not properly to feel more surprised at a species becoming extinct than at one being rare; and yet we are accustomed to view the rarity of any particular species as an ordinary event, not requiring any extraordinary agency.
The several mammifers embedded in the Pampean formation, which mostly belong to extinct genera, and some even to extinct families or orders, and which differ nearly, if not quite, as much as do the Eocene mammifers of Europe from living quadrupeds having existed contemporaneously with mollusca, all still inhabiting the adjoining sea, is certainly a most striking fact.It is, however, far from being an isolated one; for, during the late tertiary deposits of Britain, an elephant, rhinoceros, and hippopotamus co-existed with many recent land and fresh-water shells; and in North America, we have the best evidence that a mastodon, elephant, megatherium, megalonyx, mylodon, an extinct horse and ox, likewise co-existed with numerous land, fresh-water, and marine recent shells.(Many original observations, and a summary on this subject, are given in Mr.
